This invention relates to systems for finding the direction to a source of radiant energy and, more particularly, to a system employing four detectors of infrared radiation for finding the direction to an infrared source.
Direction finding equipment has been used for many years in a variety of situations such as in the locating of a source of distress signals at sea, the monitoring of unauthorized electromagnetic transmissions, and in military operations for the locating of an enemy threat. Direction finding apparatus operates in different parts of the electromagnetic spectrum, and employs detectors of electromagnetic radiation which are specialized for the portions of the spectrum being employed.
Of particular interest herein is the detection of radiation in the infrared portion of the electromagnetic spectrum, and the determination of the direction of a source of the radiation. Imaging systems operating with infrared radiation employ arrays of detectors wherein one such array employs many detectors, possibly over 100 detectors. Such arrays are scanned across a subject and produce a well-defined image wherein the directions to points of the image are well defined.
A problem arises in the case of direction finding equipment for the infrared portion of the electromagnetic spectrum in that the use of scanning arrays would be overly complex and provide far more data than is required for the establishment of a direction to a source of radiation. In addition, such scanning arrays typically view a relatively small sector of space and, therefore, would have limited utility in a direction finding environment.